1. Field of the Invention
The present invention relates to the synthesis of oligosaccharides. In particular, it relates to improved enzymatic synthesis of GDP-fucose, which can be used in fucosylation reactions. The methods make possible the synthesis of complex fucosylated oligosaccharides in a single vessel using readily available starting materials.
2. Background
Increased understanding of the role of carbohydrates as recognition elements on the surface of cells has led to increased interest in the production of carbohydrate molecules of defined structure. For instance, compounds comprising the sialyl Lewis ligands, sialyl Lewisx and sialyl Lewisa are present in leukocyte and non-leukocyte cell lines that bind to receptors such as the ELAM-1 and GMP 140 receptors. Polley et al., Proc. Natl. Acad. Sci., USA, 88: 6224 (1991) and Phillips et al., Science, 250: 1130 (1990), see, also, U.S. Ser. No. 08/063,181.
Because of interest in making desired carbohydrate structures, glycosyltransferases and their role in enzyme-catalyzed synthesis of carbohydrates are presently being extensively studied. These enzymes exhibit high specificity and are useful in forming carbohydrate structures of defined sequence. Consequently, glycosyltransferases are increasingly used as enzymatic catalysts in synthesis of a number of carbohydrates used for therapeutic and other purposes.
In the application of enzymes to the field of synthetic carbohydrate chemistry, the use of glycosyltransferases for enzymatic synthesis of carbohydrate offers advantages over chemical methods due to the virtually complete stereoselectivity and linkage specificity offered by the enzymes (Ito et al., Pure Appl. Chem., 65:753 (1993); and U.S. Pat. Nos. 5,352,670, and 5,374,541). However, the commercial-scale production of carbohydrate compounds is often complicated by the cost and difficulty in obtaining reactants that are used in the enzymatic and chemical synthesis of the carbohydrates.
Improved methods for enzymatic synthesis of carbohydrate compounds, and precursors used in these syntheses, would advance the production of a number of beneficial compounds. The present invention fulfills these and other needs.